This invention relates to dual power source networks and, more specifically, to voltage regulating power supply circuits that are operable to output a regulated dc voltage in linear and switching modes based on the status of the network. This invention also relates to dual power supply coaxial cable network monitoring systems.
As residential applications for broadband communications continue to grow, coaxial cable networks, which form the infrastructure for the majority of such systems, are being adapted for multiple uses. Such networks can be adapted to supply power to the various electronic components in residential interface units that are required for diverse broadband applications. Such applications would include cable television, telephony, and other applications that rely on broadband networks. Coaxial residential network last mile, or xe2x80x9cdropxe2x80x9d cables, supply unregulated ac power to individual homes that can be adapted by power supplies to serve a variety of needs.
Complex outdoor networks are sometimes susceptible to power interruptions, so it is advantageous to use power supplies that are able to anticipate input power fluctuations. It is known that the linear mode of operation is advantageous for minimizing noise that may cause incorrect readings for monitoring applications. Conversely, the high current requirements of normal operation are best served by the power conversion efficiency of the switching power mode. xe2x80x9cDual regulator modexe2x80x9d power supplies have the ability to switch between linear and xe2x80x9cswitchingxe2x80x9d, or xe2x80x9cpulsatingxe2x80x9d modes. An example of a dual regulator method is disclosed in U.S. Pat. No. 4,502,152 to Sinclair. Sinclair discloses the basic design of a power supply circuit that includes a high current switching regulator and a low current linear regulator feeding a common regulated output supply rail. U.S. Pat. No. 5,083,078 to Kubler is another dual regulator method adaptable, in particular, for use in motor vehicle applications. Both examples are useful for the basic purpose of dual mode operation, but do not contemplate, and are not best suited to, the variable input power adaptability requirements for a coaxial cable network because they cannot automatically switch modes of output. Also, neither Sinclair nor Kubler contemplates adjusting modes based on variations in the power source voltage magnitude.
While the dual regulator method is advantageous, circuit complexity makes such methods less reliable at producing stable outputs than conventional power supplies. Further, the complexity required for dual regulators arranged in a parallel method (as in Sinclair) causes packaging constraints. U.S. Pat. No. 5,034,676 to Kinzalow discloses a direct current power supply circuit having automatic linear and switching modes. The circuit in Kinzalow is designed using a three terminal linear voltage regulator as a control element. Specifically, the circuit is designed to operate in an environment where input to output voltage drop is less than two volts. Such capability is useful in automotive applications where the SAE measured range of an automobile alternator is within 2-5 volts of the voltage required for many automotive electronics. While Kinzalow is suitable for it""s intended purpose of supplying loads that require narrowly different power levels from those supplied from a singular relatively constant magnitude unregulated source, it does not improve upon higher magnitude conversion, or xe2x80x9cstep downxe2x80x9d methods suitable to regulate (or monitor) dual power source networks drop cables. Kinzalow is designed to adapt to the changing power requirements of the load (e.g., power requirement differences between regular operation and standby and monitoring modes) rather than variations in the power source.
It is further noted that speed is critical for adapting to power source variations. U.S. Pat. No. 5,548,204 to Armstrong II discloses a method for a linear/switching regulator circuit that is implemented by a reconfigurable integrated circuit. While the invention can be reconfigured to accommodate various loads, the complexity involved in implementing a reconfigurable integrated circuit chip has a possible unintended effect of reducing the accuracy of voltage measurements and thus, could adversely affect response time. Armstrong II, like Kinzalow, is also configured to respond to variation in the load rather than the power source.
Therefore, there is a need in the art for a voltage regulating power supply system that is operable to output a regulated dc voltage in linear and switching modes based on the status of a dual power source coaxial cable network.
There is also a need in the art for a small size, low current power supply that can efficiently convert power for use by home utility interfaces from an unregulated power source such as a coaxial residential network drop cable, thus eliminating the need to draw power from a conventional power grid.
Finally, there is a need in the art for a small size, low current power supply that is able to detect a dual power source coaxial cable network""s operating status and automatically switch between a pulsating mode, for normal operations when high efficiency power conversion is necessary, and a linear mode, for monitoring when a primary power source becomes disconnected from the network, based on the detected status.
The present invention overcomes the above described problems in the prior art by providing a dual power source coaxial cable network mode regulating system for determining whether a power source is present. The present invention consists of a primary power source for producing a first voltage and a secondary power source for producing a second voltage. A common input combines the first voltage with the second voltage. A circuit produces an output voltage in either linear mode or pulsating mode based on the magnitude of the combined first and second voltages received from the common input.
Objects, features and advantages of the present invention will become apparent upon reading the following detailed description of the preferred embodiments of the invention, when taken in conjunction with the accompanying drawings and the appended claims.